指數方程式的問題

\(\begin{align}
  & {{b}^{2}}+1=7b \\
& b+\frac{1}{b}=7 \\
& {{b}^{2}}+\frac{1}{{{b}^{2}}}={{\left( b+\frac{1}{b} \right)}^{2}}-2=47 \\
\end{align}\)